SSP3: AIM Implementation of Shared Socioeconomic Pathways

Shinichiro Fujimori, Tomoko Hasegawa, Toshihiko Masui, Kiyoshi Takahashi, Diego Silva Herren, Hancheng Dai, Yasuaki Hijioka, and Mikiko Kainuma


SSP3: AIM Implementation of Shared Socioeconomic Pathways

著者:Shinichiro Fujimori, Tomoko Hasegawa, Toshihiko Masui, Kiyoshi Takahashi, Diego Silva Herren, Hancheng Dai, Yasuaki Hijioka, and Mikiko Kainuma

掲載雑誌:Global Environmental Change


より詳細:(報道発表)気候変動研究で分野横断的に用いられる社会経済シナリオ(SSP; Shared Socioeconomic Pathways)の公表(お知らせ)


 本研究はAIM/CGE (Asia-Pacific Integrated Assessment/Computable General Equilibrium)という統合評価モデルを用いて共通社会経済シナリオShared Socioeconomic Pathways (SSPs)を定量化しました。SSPsにはSSP1からSSP5までの5つのシナリオがありますが、その中でSSP3 (地域分断シナリオ)が本研究の主要な論点で、このシナリオは緩和策も適応策も困難シナリオという特徴があります。これはAIMモデルがSSP3のマーカーシナリオ に選ばれたためです。複数のモデル内パラメータをSSPによって異なるように想定して、定量化を行いました。そして、SSP3の定量的シナリオが叙述的シナリオと整合的であるということを確認しました。さらに、4つの重要な特徴がSSP3にはあることが確認されました。第一に、SSP3は緩和策への困難性が高いことから緩和費用が高いということです。第二に、SSP3のベースラインのCO2排出量はSSP2と異なりましたが、2100年の放射強制力はSSP2とほぼ同じでした。これは主としてSSP3でエアロゾル排出量が多いためです。第三に大気汚染物質排出規制が弱いため、それらの排出量が大きいことです。第四に耕作地、牧草地が拡大し森林減少が大きかった。

This study quantifies the Shared Socioeconomic Pathways (SSPs) using AIM/CGE (Asia-Pacific Integrated Assessment/Computable General Equilibrium). SSP3 (regional rivalry) forms the main focus of the study, which is supposed to face high challenges both in mitigation and adaptation. The AIM model has been selected as the model to quantify the SSP3 marker scenario, a representative case illustrating a particular narrative. Multiple parameter assumptions in AIM/CGE were differentiated across the SSPs for quantification. We confirm that SSP3 quantitative scenarios outcomes are consistent with its narrative. Moreover, four key features of SSP3 are observed. First, as SSP3 was originally designed to contain a high level of challenges to mitigation, mitigation costs in SSP3 were relatively high. This results from the combination of high greenhouse gas emissions in the baseline (no climate mitigation policy) scenario and low mitigative capacity. Second, the climate forcing level in 2100 for the baseline scenarios of SSP3 was similar to that of SSP2, whereas CO2 emissions in SSP3 are higher than those in SSP2. This is mainly due to high aerosol emissions in SSP3. A third feature was the high air pollutant emissions associated with weak implementation of air quality legislation and a high level of coal dependency. Fourth, forest area steadily decreases with a large expansion of cropland and pasture land. These characteristics indicate at least four potential uses for SSP3. First, SSP3 is useful for both IAM and impact, adaptation, vulnerability (IAV) analyses to present the worst-case scenario. Second, by comparing SSP2 and SSP3, IAV analyses can clarify the influences of socioeconomic elements under similar climatic conditions. Third, the high air pollutant emissions would be of interest to atmospheric chemistry climate modelers. Finally, in addition to climate change studies, many other environmental studies could benefit from the meaningful insights available from the large-scale land use change resulting in SSP3.